What it is:  LumenMill is an application for Windows (10/11) or Mac (???) which connects to a Bluetooth heart rate monitor and obscures the screen with a filter if your heart rate is too high or too low, subject to your specifications.  A heads-up-display shows your heart rate, duration, and other data over the top of whatever entertainment you have chosen to numb the pain and boredom of stationary cardiovascular exercise.  By default, if your heart rate drops below a user-specified level, the screen and sound will be gradually obscured by old-school TV static.  If your heart rate goes above a user-specified level, the screen will gradually go red and an alarm tone will get louder.  The sound, the color and how quickly they kick in are all user-customizable.  

Demonstration Video – start in zone, drop below, then sprint

How it works:  When you open LumenMill, a “preview” window is presented.  Click anywhere on it to connect to the heart rate monitor, adjust and save settings, and control the operation through a simple menu .  After you connect to your chosen heart rate monitor, it will present a preview of what the filter and HUD will look like once activated.  When you are ready to start exercising, turn on the HUD, Video and/or audio, select whatever window your entertainment is on and start exercising.  When you are ready to stop, just reselect the preview window and click anywhere to bring up the menu.

Demonstration of window operation.

In Windows, LumenMill will obscure all windows, even maximized ones.  On MacOS, LumenMill can’t obscure maximized windows, so you just have to adjust the window size manually (this is just a feature of MacOS, and almost certainly not my lack of programming prowess.)

How much it costs:  LumenMill is $11.99 per year, with a 24-hour trial period.  It’s available on the Windows Store and Apple App Store.